Right, here go's , my sole theory , say the north Atlantic drift , the northern portion of the amoc, has had over the last few years an infusion of fresh water , this year particularly large, now if this has slightly diluted sub surface layers via interwoven fresh too salination , during summer not noticeable , but as winter rolls on, buy my understanding the jet stream follows warm cold corridor seasonal variations, if you , say cut surface connection at sea level , then as cold intensifies the jet stream would lose it's connection too surface. As the colder dense pool wouldn't have surface resistance , therefore would correct south, as temperature anomalies would suggest, in my humble view this should be looked at , theory .